Making New Connections: How the Brain Can Develop Into Adulthood

By Alice G. Walton

A multi-year study has found that the brain's white matter -- fibers connecting cells -- can shift with employment, education, and relationships

For many years, the convention was that after adolescence, the brain had done about as much developing as it was going to do. Recent research has changed that notion, however, with studies finding that the brain can actually grow new neurons
in certain areas. Now, a group reports that the fiber tracks
connecting brain cell to brain cell (the white matter of the brain) may
also continue to develop into early adulthood.

The team of researchers scanned participants'
brains using magnetic resonance imaging (MRI) at two time points or
more. At the beginning of the study, the participants ranged in age
from 5 to 29, and the average gap between the first and second scanning
was about four years. They focused on 10 white-matter tracts in the
frontal lobes of the participants' brains, monitoring how they changed
over the study period.

They found that two types of connections -- projection tracts,
which connect the cortex to other parts of the brain and spinal cord,
and commissural tracts, which connect the two hemispheres of the brain -- did not change after adolescence. But association tracts, which
connect different regions within one side of the brain, continued to
proliferate into early adulthood for up to half of the participants.

The frontal lobe is responsible for
high-level executive function and attention. The authors suggest that
this frontal lobe "postadolescent development may be influenced by
complex and demanding life experiences such as advanced education,
full-time employment, independence, and new social/family
relationships." Since the structure of the brain can change in response
to learning experiences, they say, it's feasible that "life lessons"
could shift connections in similar ways.

Another notable finding was that in a minority of people, the white
matter tracts actually diminished with time, which could be linked to
brain degeneration or psychiatric problems. The white matter in the
frontal lobe is known to be underdeveloped in people with mood
disorders, anxiety, and schizophrenia, which often develops by young
adulthood.

Study author Christian Beaulieu says that "a lot of psychiatric
illness and other disorders emerge during adolescence, so some of the
thought might be if certain tracts start to degenerate too soon, it may
not be responsible for these disorders, but it may be one of the factors
that makes someone more susceptible to developing these disorders."

More work is needed to follow up on the idea that brain changes could
be markers of problems to come. But the fact that our brains continue
to mature into early adulthood shows once again that the brain is more plastic than previously thought, which researchers are just beginning to illustrate in detail.

The study was carried out at the University of Alberta, and published in the July 27, 2011, issue of the Journal of Neuroscience.

Image: Connections between brain cells proliferate between two time points/Journal of Neuroscience.